<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
    //     new Promise((resolve,reject) =>{
    //     setTimeout(() =>{
    //         resolve('helloworld')
    //         reject('error message')
    //     },1000)
    // }).then().catch()


        new Promise((resolve,reject) =>{
        setTimeout(() =>{
            // resolve('helloworld')
            reject('error message')
        },1000)
    }).then(data=>{
        console.log(data);
    },err =>{
        console.log(err);
    })
    </script>
</body>
</html>